Brief Summary: RATIONALE: Biological therapies, such as fusion protein cytokine therapy, may stimulate the immune system in different ways and stop cancer cells from growing. Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. Giving fusion protein cytokine therapy together with rituximab may kill more cancer cells. PURPOSE: This phase I trial is studying the side effects and best dose of fusion protein cytokine therapy when given after rituximab in treating patients with B-cell non-Hodgkin lymphoma.

Detailed Description: PRIMARY OBJECTIVES: I. To determine the maximum tolerated dose (MTD) of DI-Leu16-IL2 (DI-Leu16-IL2 immunocytokine) following peripheral blood B cell depletion with rituximab in patients with B-cell NHL. II. To investigate the optimal biological dose (OBD) of DI-Leu16-IL2 following peripheral blood B cell depletion with rituximab in patients with B-cell NHL, which may differ from the MTD. III. To describe the toxicities associated with the proposed DI-Leu16-IL2 regimen. SECONDARY OBJECTIVES: I. To evaluate the immunogenicity as measured by the induction of DI-Leu16-IL2-specific antibodies. II. To evaluate the pharmacokinetics of DI-Leu16-IL2. III. To document any clinical responses associated with the proposed therapy and survival endpoints of the enrolled patients. OUTLINE: This is a dose-escalation study of DI-Leu16-IL2 immunocytokine. Patients receive DI-Leu16-IL2 immunocytokine IV over 4 hours on 4 consecutive Wednesdays. Patients with detectable CD20-positive B-cells pretreatment also receive rituximab IV on 4 consecutive Tuesdays. Treatment repeats every 6 weeks for up to 4 courses in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up periodically for 5 years.